Magnetic encoder with snap action switch

ABSTRACT

The disclosure is directed to an encoder apparatus that is capable of resolving magnetically axial and/or rotational displacements of a knob shaft thereof independently and includes a magnetic snap action switch, and a method of assembling the same. In one embodiment, the encoder apparatus has application as a display controller. In another embodiment, one or more of the encoder assemblies may be integrated into a bezel of a display for controlling the operations thereof.

BACKGROUND OF THE INVENTION

[0001] The present invention is directed to encoder apparatus, ingeneral, and more particularly, to an encoder capable of resolvingmagnetically axial and/or rotational displacements independently andincluding a magnetic snap action switch.

[0002] Generally, encoder switches for use in avionics, like forcontrolling various functions of a display disposed on a cockpit panel,for example, are operative in a severe environment of shock andvibration while maintaining the intended accuracy and resolution,especially over a wide temperature range. As more and more avionicinstruments are included on the cockpit panel to assist the pilot duringflight, there is a continuing push to make the instruments and theircorresponding control switches smaller while improving upon the accuracyand resolution thereof. In some instances, it may be desirable tocombine functionality of two devices into one to reduce size and weight.This is no easy chore considering the stressful environment and widetemperature ranges over which these devices are intended to operate withhigh resolution and accuracy.

[0003] For example, well known AB switch encoders are used to controlavionic instruments through rotational movement of the switch. Thesetype encoder switches operate on a purely digital basis. Generally, twomagnetic sensors are disposed within the switch in a quadratureorientation about either a cogged wheel or a multiple pole permanentmagnet that is attached to the switch shaft and rotated past themagnetic sensors. Each sensor produces a pulsed train signal A and B inquadrature to the other in response to the shaft rotation. The angularposition and direction of rotation of the switch is resolved by encodingthe pulsed signal trains A and B. In order to improve the resolution ofthese type switches, more cogs may be added to the wheel or moremagnetic poles added to the permanent magnet. This may not result in aproblem in and of itself, but to increase density and also reduce thesize of the switch introduce alignment difficulties in sensing theangular position of the shaft at the desired resolution. In theenvironment of an aircraft, for example, the shock and vibration maycause a change in the alignment of the sensor with respect to the moreclosely spaced cogs or magnetic poles to render an error in angularposition. Thus, improvement in this area is considered desirable.

[0004] Moreover, optical encoders are being proposed for use as analternative sensing mechanism to their magnetic counterparts. Whilethese optical devices may offer better resolution, they are much moresensitive to alignment and do not appear to be a viable alternative tomagnetic sensing, especially over the wide operational temperatureranges of an aircraft not to mention the severe vibration and shockenvironments thereof. In addition, the packaging of these opticalencoders are not currently designed to provide the necessary protectionover the wide operating temperature ranges of an aircraft environment.

[0005] Devices that are used to detect axial displacement of the switchshaft, like push switches, for example, currently use a flexible domedelement in the base of the switch to offer a “snap action” feel to theoperator. When the switch is depressed, the bottom of the shaft makescontact with and flexes the top of the domed element and when the switchis released, the domed element flexes back to its original shape forcingthe shaft to spring upward. Over time and with use, the mechanical domedelement loses elasticity or collapses in shape, thus causing a loss inthe “snap action” feel. This is another area where improvement appearsdesirable.

[0006] As has been indicated above, there is also a push to combinefunctionality in these avionic control switches and as a result of thispush, it is desired to combine the functions of axial and rotationaldisplacement in the same assembly with an improved resolution andaccuracy. A multifunctional encoder of this type with improvedresolution would be considered an advance to the current state of theart of encode type switching and very desirable. Accordingly, thepresent invention intends to over come the aforementioned drawbacks ofthe current technology in the state of the art encoder and switchingmechanisms and satisfy the packaging and performance demands for futureapplications, especially for avionic instruments.

SUMMARY OF THE INVENTION

[0007] In accordance with one aspect of the present invention, a switchwith magnetic snap action comprises a housing, at least one permanentmagnet fixedly disposed with respect to the housing in a cavity of thehousing, and a knob shaft including a top portion that is slideablydisposed through an opening in the housing, and a bottom portiondisposed in the housing cavity and including a member comprised of amagnetically attractive material. The knob shaft is held axially in afirst position by a magnetic force between the shaft member and the atleast one permanent magnet in the housing cavity. The knob shaft isdisplaced from the first position for as long as the magnetic force isovercome by an external force applied to the knob shaft, where uponrelease of the external force, the knob shaft snaps back to the firstposition by the magnetic force. A method of assembling the switchcomprises the steps of: creating a first opening in a bottom side of thehousing and a cavity within the housing into which the first openingextends, creating a second opening in a top portion of the housing whichextends to the cavity, the second opening being smaller in width thanthe first opening, affixing a flux washer around an inner periphery ofthe cavity through the first opening, disposing a top portion of abushing through the first opening, the cavity and through the secondopening of the housing to render a bottom portion of the bushing withinthe flux washer, disposing a plurality of permanent magnets into cutoutsaround the periphery of the bottom portion of the bushing in an annularspace between the bottom portion and the flux water, and disposing a topportion of a knob shaft though the first opening, the cavity and anopening in the bushing to render a disked shaped member of a bottomportion of the knob shaft comprised of a magnetic material injuxtaposition with the bottom portion of the bushing and form a magneticconnection with the plurality of permanent magnets thereof.

[0008] In accordance with another aspect of the present invention, aswitch with magnetic snap action comprises a housing, a plate ofmagnetically attractive material fixedly disposed at an inside peripheryof a cavity of the housing, and a knob shaft including a top portionthat is slideably disposed through an opening in the housing, and abottom portion disposed in the housing cavity and including a permanentmagnet. The knob shaft is held axially in a first position with respectto the housing by a magnetic force between the permanent magnet and theplate. The knob shaft is slideably displaceable from the first positionfor as long as the magnetic force is overcome by an external forceapplied to the knob shaft, whereby upon release of the external force,the knob shaft snaps back to the first position by the magnetic force.

[0009] In accordance with yet another aspect of the present invention,an encoder apparatus comprises a housing, a knob shaft including anupper portion disposed through an opening in the housing, and a lowerportion disposed in a cavity of the housing and including a permanentmagnet magnetized with at least one set of north-south magnetic poles,the knob shaft and its permanent magnet being rotateably moveable in thehousing cavity, a plurality of magnetic filled sensors disposed withinthe housing cavity in proximity to the permanent magnet and distributedangularly thereabout to sense the magnet field strength of the permanentmagnet based on the orientation of the permanent magnet with respect tothe sensors, each sensor for generating a signal representative of themagnitude of the magnetic field strength sense thereby, and a processorfor processing the sensor signals to resolve rotational movement of theknob shaft. In accordance with still another aspect of the presentinvention, a multifunctional encoder apparatus comprises a housing, aknob shaft including an upper portion disposed through an opening in thehousing and a lower portion disposed in a cavity of a housing andincluding a permanent magnet magnetized with at least one set ofnorth-south magnetic poles, said knob shaft and it's permanent magnetbeing axially and rotatably moveable in the housing cavity, a pluralityof magnetic field sensors disposed within the housing cavity inproximity to the permanent magnet and distributed angularly thereaboutto sense the magnetic field strength of the permanent magnet based onthe orientation of the permanent magnet with respect to the sensors,each sensor for generating a signal representative of the magnitude ofthe magnetic field strength sensed thereby, and a processor forprocessing the sensor signals to independently resolve axial androtational movement of the knob shaft.

[0010] In accordance with still another aspect of the present invention,a controller for a display comprises at least one multifunctionalencoder including a housing, a knob shaft including an upper portiondisposed through the housing opening, and a lower portion disposed in acavity of the housing and including a permanent magnet magnetized withat least one set of north-south magnetic pulls, the knob shaft and itspermanent magnet being axially and rotateably moveable in the housingcavity, and a plurality of magnetic field sensors disposed within thehousing cavity in proximity to the permanent magnet and distributedangularly thereabout to sensed the magnetic field strength of thepermanent magnet based on the orientation of the permanent magnet withrespect to the sensors, each sensor for generating a signalrepresentative of the magnitude of the magnetic field strength sensedthereby, and a processor governed by the sensor signals to generatecontrol signals for controlling the display area.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGS. 1A-1E are cross-sectional illustrative views of andexemplify a method of assembling a multifunctional encoder apparatusincluding a switch arrangement with magnetic snap action suitable forembodying the principles of the present invention.

[0012]FIG. 2 depicts bottom, side and top views of a bushing suitablefor use in the embodiment of FIG. 1.

[0013]FIG. 3 depicts bottom, side and top views of a shaft suitable foruse in the embodiment of FIG. 1.

[0014]FIG. 4 is a prospective view of a bushing with permanent magnetsaffixed to cutouts thereof suitable for use in the embodiment of FIG. 1.

[0015]FIG. 5 is an illustrative prospective view of the encoderapparatus a detent mechanism suitable for use in the embodiment of FIG.1.

[0016]FIG. 6 is another illustrative prospective view of the encoderapparatus showing another aspect of the detent mechanism suitable foruse in the embodiment of FIG. 1.

[0017]FIG. 7 is a prospective view of the encoder apparatus illustratingthe operation of the embodiment of FIG. 1.

[0018]FIG. 8 is a block diagram schematic suitable for embodying one ormore aspects of the present invention.

[0019] FIGS. 9A-9C depict a flow chart which is suitable for use inprogramming the digital processor of the embodiment of FIG. 8.

[0020]FIG. 10 is a graph which illustrates the operation of the encoderapparatus in accordance with the flow charts of FIGS. 9A-9C.

[0021]FIG. 11 is a cross-section view of an encoder apparatus suitablefor embodying another aspect of the present invention.

[0022]FIG. 12 depicts a top view and cross-sectional side views of adisplay bezel including two encoder assemblies suitable for use inembodying yet another aspect of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] FIGS. 1A-1E are cross sectional illustrative views of amultifunctional encoder apparatus including a switch arrangement withmagnetic snap action and exemplify a method of assembling the same. InFIG. 1A is shown a housing 10 having top 12 and bottom 14 sides. A firstopening 16 in the bottom side 14 and a cavity 18 are created within thehousing 10. A second opening 20 is created in the top portion 12 of thehousing and extends down into the cavity 18, the second opening 20 beingsmaller in size than the first opening 16. In the present embodiment,the first opening 16, the second opening 20, and the cavity 18 are allcylindrical in shape. However it is understood that these sections ofthe housing may take upon any shape without deviating from theprinciples of the present invention.

[0024] In FIG. 1B, a flux member 22 is affixed to the inner periphery ofthe cavity through the first opening 16 of the housing 10. The fluxmember 22 which may be comprised of a magnetically attractive material,such as Nickel plated, 018 cold finished Steel, for example, is shapedas a washer and may be press fitted into the cavity 18 through theopening 16. Next, as shown in FIG. 1C, a bushing 24 including a topportion 26 that is disposed through the opening 16, the cavity 18, andthrough the housing opening 20 extending beyond the top side 12, and abottom portion 28 that remains in the cavity 18 and includes at leastone permanent magnet. In the present embodiment, the bushing 24accommodates a plurality of permanent magnets 30 that may be disposedthrough the opening 16 into cutouts around the periphery of the bottomportion 28 in an annular space between the bottom portion 28 and aninner wall of the housing cavity 18 resting against the flux washer 22.The bushing 24 also includes a hollow opening 32 centrally located andextending axially therethrough from the bottom portion 28 to the topportion 26.

[0025] A more detailed depiction of the bushing 24 is shown by thebottom 40, side 42 and top 44 views of FIG. 2. Referring to FIG. 2, thebottom portion 28 includes cut-outs 46 uniformly spaced around itsperiphery to accommodate the plurality of permanent magnets 30 (notshown) which are to be affixed thereto. In addition, the top portion 26of the bushing 24 includes cut outs 48 disposed about the peripherythereof to accommodate a plurality of ball bearings (not shown). In thepresent embodiment, the cut outs 48 permit the ball bearings to protruderadially through the wall of the bushing and into the opening 32 asshown in the cutaway top view 44. In the present embodiment, the cutouts 48 are in the form of radial holes distributed uniformly in atleast one row 50 around the periphery of the top portion 26 of thebrushing 24. The embodiment depicted in FIG. 2 illustrates two rows 50and 52 of the radial holes 48. The use of these radial holes 48 in thepresent embodiment will become more apparent from the description supra.

[0026] Referring to FIG. 4, perspective view of the bushing 24 isillustrated in which four permanent magnets 30 are affixed contiguouslyto each of four cut outs 46 in the bottom portion 28 thereof. In thepresent embodiment, the permanent magnets 30 are arranged around theperiphery of the bottom portion 28 so that the North and South Polesthereof are axially aligned with the axis of the bushing in analternating magnetic pattern around the periphery thereof. The permanentmagnets 30 may be affixed to the cut outs 46 in the bottom portion 28 byan adhesive or the like. Referring back to FIG. 1C, the bottom portion28 of the bushing 24 and its magnets 30 are disposed within the width ofthe flux washer 22 such that the permanent magnets 30 are held fixedlyin axial position with respect to the housing 10 by magnetic attractionto the flux washer 22.

[0027] Next, as shown in FIG. 1D, a knob shaft 60 including a topportion 62 and a bottom portion 64 is assembled to the housing 10 andbushing 24. In the present embodiment the top portion 62 of the shaft 60is disposed through the first opening 16, the cavity 18 and the bushingopening 32 to render the bottom portion 64 within the housing cavity 18.The bottom portion 64 includes a member 66 comprised of a magneticallyattractive material, such as a Ferrous material, for example, that isheld in place in juxtaposition with the bottom portion 28 of the bushing24 by a magnetic attraction force of the permanent magnets 30 thereof.In other words, the member 66 of the shaft 60, the permanent magnets 30and the flux washer 22 together form a complete magnetic connection. Inthe present embodiment as shown in FIGS. 1D and 4, a small gap, on theorder of 0.005 inches, for example, is maintained between the magnets 30and the member 66 in order to avoid rubbing, friction and general wearand tear of the magnets 30 as the member 66 is rotated across the bottomportion 28 of the bushing 24. Also, in the bottom portion 64 of theshaft 60, under the member 66 is a shaft layer 68 comprised of anon-ferrous or magnetically insulating material and under that is asmall permanent magnet 70. The small permanent magnet 70 may bemagnetized parallel to the diameter thereof and includes at least oneset of North-South Poles which are transverse to the axis of the shaft60. However, it is understood that the permanent magnet 70 may bemagnetized in other orientations without deviating from the presentinvention.

[0028] The shaft 60 is shown in greater detail in the bottom 74, side76, and top 78 views of FIG. 3. Referring to FIG. 3, at the very top ofthe shaft 60 is a member 80 which extends above the bushing 24 when theshaft is inserted through the opening 32 thereof (refer to FIG. 1D). Themember 80 is shaped to accommodate a knob (not shown) for operating theencoder. It may be slotted, keyed or include a through-hole for a rollpin, for example. Also, the top portion 62 of the shaft 60 includes aplurality of axial grooves 82 disposed around the periphery thereof. Thegrooves 82 are positioned axially on the top portion 62 of the shaft 60to be aligned with the radial holes 48 of the bushing 24 to provide adetent communicating mechanism therebetween. As shown in the perspectiveview of FIG. 5, ball bearings 84 are disposed in their respective radialholes 48 in the rows 50 and/or 52 of the top portion 26 of the bushing24.

[0029] More specifically, the ball bearings 84 protrude radially throughthe holes 48 of the bushing 24 and come in contact with the axialgrooves as the knob shaft 60 is rotated in the opening of the bushing24. In the present embodiment, the ball bearings 84 are held in place inthe radial holes 48 by O-rings 86 as shown in the perspective view ofFIG. 6. The O-rings 86 both contain the balls 84 in the radial holes 48and also apply an inward radial force on the balls 84 engaging them withthe shaft and grooves 82. Accordingly, as the shaft is rotated in theopening 32 of the bushing 24 some of the ball bearings 84 will be forcedinto the slots 82 of the shaft causing a detent position.

[0030] In the present embodiment, the knob shaft includes nine groovesor slots 82, parallel to the shaft's axis of rotation and distributeduniformly around the periphery or circumference of the shaft 60. Inaddition, the bushing 24 has six radial holes per row 50 or 52 which aredistributed uniformly around the circumference thereof. When the knobshaft 60 is in a detent position with the bushing 24, only three of theballs will be fully engaged in the slots 82 of the shaft 60. If theshaft is rotated one detent position in either direction, the otherthree balls will be engaged and the previous three balls will no longerbe fully engaged. This combination generates 18 detent positions perrevolution of the shaft, that is two ball sets times nine slots. If ahigher knob rotation torque is required, another set of six balls can beadded in another row, say 52, for example, thus doubling the torque. Inaddition, if a higher detent count is needed, the second row of sixballs can be offset from the first row of six generating thirty-sixdetents per revolution, that is four ball sets times nine slots.

[0031] Returning now to FIG. 3, in the present embodiment, the member 66of the bottom portion 64 of the shaft 60 is comprised of a ferrousmaterial and is disc shaped having a diameter large enough to allow thedisc member 66 to form a magnetic connection with the permanent magnets30 of the bushing 24. The disc like member or shaft plate 66 is held incontact with the bottom 28 of the bushing 24 by the magnetic attractionforce between it and the permanent magnets 30 in the cavity 18 of thehousing 10 as shown in FIG. 1D and also in FIG. 4. In the presentembodiment, the four permanent magnets 30 are of a high energy-productmagnet type which may be comprised of a Samarium Cobalt material, forexample. Accordingly, the disc or plate 66 is attracted to the permanentmagnets 30 of the bushing 24 with a relatively high magnetic attractionforce.

[0032] Referring to FIG. 1E, a stop member 88 may also be disposed inthe housing cavity 18 to serve as a stop to the displacement of theshaft member 66. In the present embodiment, the member 88 is comprisedof a ferrous material, like 066 cold rolled Steel, for example, and maybe ring like in shape for insertion around the inner periphery of thecavity 18 to contain the magnetic field of the permanent magnet withinthe cavity 18 and act as a shield to any extraneous external magneticfields.

[0033] Thus, in operation, when an external force is applied to the topend of the knob shaft 60 to depress the shaft into the cavity 18 of thehousing 10, the magnetic attraction force of the permanent magnets 30 onthe shaft member 66 resists the depressive push on the shaft until theexternal force overcomes the magnetic attraction force or forcethreshold. Once the force threshold is reached, the knob shaft 60slidably moves or is displaced downward in the opening 32, increasingthe gap 90 between the permanent magnet 30 and shaft plate 66 such asthat shown in the illustration of FIG. 7. As the gap 90 increases, themagnetic attraction or pull force of the permanent magnets 30 isreduced. Accordingly, the magnetic attraction force drops off withdisplacement, i.e. the gap 90, permitting the knob shaft to travel to afully depressed position resulting in a “snap action” feel. When theexternal force on the knob shaft is released, the magnetic attraction orpull force generated by the permanent magnets 30 on the shaft 66 willsnap the shaft back to its juxtaposed position with the bushing 24. Thatis, the shaft plate member 66 will be in full contact with the bushingportion 28 as shown in the illustration of FIG. 4.

[0034] While this aspect of the present invention is exemplified using apush switch embodiment as described hereabove, it is understood that bysimply rearranging the switch elements that the same inventiveprinciples will also apply to a pull switch. Moreover, while anattractive magnetic force is used in the exemplary embodiment describedabove, it is further understood that a repulsive magnetic force could beused just as well by a rearrangement of members without deviating fromthe principles of the present invention.

[0035] Referring back to FIG. 1E, the knob shaft 60 and its permanentmagnet 70 are axially and/or rotatably moveable in the housing cavity18. A plurality of magnetic field sensors 94 are disposed within thehousing cavity 18 in proximity to the permanent magnet 70 of the shaft60 and distributed angularly thereabout to sense the magnetic fieldstrength of the permanent magnet 70 based on the orientation thereofwith respect to the sensors 94. Each sensor 94 is capable of generatinga signal representative of the magnitude of the magnetic field strengthsensed thereby. In the present embodiment, two magnetic field sensorsare distributed about the permanent magnet 70, ninety degrees apart. Themagnetic field sensors 94 may include Hall Effect devices that may befixed in their respective positions and orientations with respect to thepermanent magnet 70 in the cavity 18, as illustrated in FIG. 1E and alsoin FIGS. 4 and 7, by their disposition on a printed circuit board 96which may be affixed to the housing 10 at the opening 16 thereof asshown in FIG. 1E. While the sensors 94 are shown upright or vertical tothe axis of the shaft 60, it is understood that other orientationsthereof such as laying the sensors flat on the printed circuit board 96will result in satisfactory sensor measurements in accordance with theprinciples of the present invention. In addition, while only two sensorsare used for the present embodiment, it is also understood that morethan two sensors may be distributed about the permanent magnet 70 forgreater accuracy or redundancy, if desired, without deviating from thepresent invention.

[0036]FIG. 8 is a block diagram schematic illustration of amultifunctional encoder apparatus employing the same aspects of theembodiment described in connection with FIGS. 1-7 hereabove. Forexample, the shaft 60 of the encoder mechanism may have affixed theretoa knob 97 which may be used to rotate the shaft 60 about its axis 98. Inaddition, the knob 97 may be depressed and released to cause the shaftto undergo axial movement along the axis 98 with respect to the encoderhousing 10 as explained hereabove. The magnetic field strength ofpermanent magnet 70 is sensed by each of the sensors 94 and theresultant signals, depicted as X and Y, are output from the sensors 94for processing by a processor 100. In the present embodiment, the sensorsignals X and Y are analog and change in amplitude according to asinusoidal waveform as the permanent magnet 70 is rotated through a 360°angular change. The sinusoidal amplitude envelopes of signals X and Yare 90° out of phase from each other throughout the 360° rotation of themagnet 70. In addition, the processor 100 may include a programmeddigital processor 102, for example. Accordingly, the analog signals Xand Y are digitized by a digitizer 104 in order to be processed in thedigital processor 102.

[0037] It is understood that the present invention should not be limitedto the use of a digital processor and it is clear to all those skilledin the pertinent art that an analog processor may be used just as wellfor performing the functions of the multifunctional encoder as describedhereinbelow. Also, it is understood that any digitizer may be used forthe processor 100 including that which is manufactured by LinearTechnology bearing model no. LTC1598, for example. Also, the programmeddigital processor 102 may be of the type manufactured by TexasInstruments bearing the model no. TMS320C31, for example. The digitizer104 of the present embodiment may digitize the analog signals X and Y atpredetermined time intervals as controlled by the digital processor 102using the select and control lines 106 in a conventional manner. In thealternative, the digitizer 104 may be adjusted to autonomously sampleand digitize the analog signals X and Y and interrupt the digitalprocessor 102, over interrupt line 108 when the digitized sensor data isavailable. In either case, the digitized sensor data signals areprovided to the digital processor 102 from the digitizer 104 over thedata lines 110.

[0038] The processor 100 may be programmed for processing the sensorsignals X and Y to independently resolve axial and rotational movementof the knob shaft 60 with respect to the housing 10. A flowchartsuitable for use in programming the digital processor 102 is shown inFIGS. 9A through 9C. In the present embodiment, the routines of FIGS.9A-9C are executed in the digital processor 102 every N milliseconds.Referring to FIG. 9A, program execution commences at the instructionblock 120 which causes the digitizer 104 to sample and digitize theanalog signals X and Y and store the digitized sensor data intoappropriate designated registers of the digital processor 102. If theanalog signals X and Y generated by the sensors 94 are unipolar withrespect to a ground reference of the encoder system, for example, then,in block 122 the digitized signals X and Y are converted to bipolar datasignals by offsetting each with an appropriate reference signal. Next,the magnitude of the magnetic field strength of the permanent magnet 70in its present orientation with respect to the sensors 94 is calculatedin block 124 by taking the square root of the sum of the squares of thedigitized signals X and Y.

[0039] In the decisional blocks 126 and 128, the processor 102determines axial movement of the shaft from a change in the magneticfield strength magnitude. This is accomplished in the present routine bycomparing the ratio of the present magnitude PM and last magnitude LM toa set of high and low limits. If the ratio is greater than the highlimits as determined by the decisional block 126, then the knob shaft isdetermined to have been depressed in the downward direction and as aresult of this determination, a push count in a designated register ofthe digital processor 102 is incremented in block 130. On the otherhand, if the ratio is determined to be below the lower limit by thedecisional block 128, then the shaft 60 is determined to have beenreleased and snapped back to its original state. Under this determinedcondition, a release count in a designated register of the digitalprocessor 102 is incremented in block 132. If neither decisional block126 nor 128 results in an affirmative decision, blocks 130 and 132 areby-passed and neither push count nor release count is incremented.Thereafter, programmed execution continues in block 134. Also, afterexecution of either block 130 or 132 is complete, program executioncontinues at block 134.

[0040] In block 134, the present quadrant of the rotational angle θ ofthe shaft is determined using the signs of the bipolar sensor signals Xand Y. An explanation of this determination is provided with referenceto the graphical illustration of FIG. 10. Note that if the signs of bothX and Y are positive the rotational angle θ is in the quadrant 0 and ifboth are negative, θ is in the quadrant II . In addition, if X isnegative and Y is positive, θ is in quadrant I and if the reverse istrue than the rotational angle θ is in quadrant III. Thus, by looking atthe signs of the digitized bipolar sensor signals, the present quadrantof the angle θ may be determined.

[0041] Returning back to FIGS. 9A-9C, if the present quadrant PQ is thesame as the last quadrant LQ as determined by the Block 136, then theangle has not moved outside of its quadrant in N milliseconds andprogram execution continues at block 138. However, if it is determinedin the decision of block 136 that PQ≠LQ, then the quadrant of angle θhas changed and the present quadrant is next determined. Decision block140 determines whether or not the present quadrant is in an adjacentquadrant AQ to the last quadrant. If it is not, the program ignores thechange and assumes no movement and execution continues at Block 138.Under this condition, a fault bit may be set to indicate a part failureor overspeed in the rotation of the shaft.

[0042] Should it be determined that the present quadrant is in anadjacent quadrant, then it is next determined by the decisional Block142 whether the rotational angle has moved clockwise or counterclockwise. For example, if the last quadrant was 0 and the presentquadrant is I, then the rotational angle is determined to have changedcounter clockwise and as a result program execution is continued inprogram block 144 wherein a quad count in a designated register of thedigital processor 102 is decremented. On the other hand, if the lastquadrant is 0 and the present quadrant is III, then the change inquadrant of the rotational angle is determined to be clockwise whereuponprogram execution continues at block 146 wherein the quad count isincremented. Thereafter, program execution continues at block 138.

[0043] For bookkeeping purposes, block 138 sets LM to a moving averageof the previously calculated magnitudes and sets LQ equal to PQ. Next,in block 150, it is determined if a M millisecond time boundary has beenreached. Such a time boundary could be, for example, two or more of theN millisecond time intervals. If the decisional block 150 determinesthat the time boundary has been reached, then, in instruction block 152,the rotational angle θ is computed as the arc tangent of the ratio ofthe digitized sensor signals Y to X. Also, in block 152 a totalrotational angle θ_(T) is calculated by multiplying the present quadrantnumber Q by 90° and adding to it the computed rotational angle θ. Alsoin 152, the change in rotational angle Δθ is calculated by subtractingfrom θ_(T) a reference angle θ_(R) which according to the presentroutine is the total rotational angle calculated during the lastexecution of the program routine or last execution of the block 152.

[0044] Next, in decisional blocks 154 and 155, it is determined whetheror not Δθ is greater than some positive predetermined angle change orless than some negative predetermined angle change in order to determineif the current rotation has exceeded a detent position. In the presentembodiment, since there are eighteen detent positions spaced uniformly20° apart around the periphery of the knob shaft, the positive andnegative predetermined angle changes are set respectively to 11° and−11°, which are slightly greater than one-half of the detent rotationalangle increment of the present embodiment in clockwise andcounterclockwise directions. It is understood that for otherarrangements, the detent angular increment, and thus, the positive andnegative predetermined angle changes, may be different.

[0045] If Δθ>11°, then a number of detent positions, ΔDetents, coveredby the angle change Δθ is determined in block 156 by subtracting 11°from Δθ and dividing the difference by 20°, then adding a one to theresult. Also in block 156, a knob rate is computed by multiplying theproduct of the current knob rate by 0.9 and adding to that result aproduct of ΔDetents and 0.1. If Δθ<−11°, then a number of detentpositions, ΔDetents, covered by the angle change Δθ is determined inblock 157 by adding 11° to Δθ and dividing the difference by 20°, thensubtracting a one from the result. Also in block 157, a knob rate iscomputed by multiplying the product of the current knob rate by 0.9 andsubtracting from that result a product of ΔDetents multiplied by 0.1. IfΔθ is determined to be between 11° and −11°, then no new detent has beenreached by the rotation, and only a new knob rate is determined in block158 as the current knob rate multiplied by 0.9.

[0046] The knob rate term that is calculated in blocks 156 and 157 is avalue that approximates the rate at which the knob is being turned,filtered with a low pass filter, i.e. 0.9×knob rate ±(ΔDetents×0.1). Inthe present embodiment, ΔDetents is used as a measure of the rate atwhich the knob is being turned. Thus, a large number of detentsindicates a high rate of turning and accordingly, a small number ofdetents indicates a low rate of turning. In addition, the rate filteringcan have a different time constant, i.e. different coefficients, forincreasing and decreasing rates depending on user preferences. This knobrate term can be used by any system that uses the knob count, i.e. thecount going through the detents, as an input to increase the gain of theknob count. For example, in a system where a user uses knob rotation asmeans of adjusting some parameter over a large range quickly yet havefine control, the knob rate is adjusted automatically to increase the“gain” of the knob count in block 156. At high rates of knob turning,the knob rate could be adjusted automatically in gain by a factor ofthree, for example, resulting in a count change per detent of threeinstead of one. However, at low rates of knob turning, the knob rateterm is adjusted downward in block 157 resulting eventually in a gain ofjust one. If one knob is used for various user inputs, each user inputmode can have its own filter and knob rate coefficients to optimize theuser interface for each type of input.

[0047] After execution of either block 156, 157 or 158, the programcontinues at block 160 wherein a new reference angle θ_(R) is calculatedby adding to the current θ_(R) the product of ΔDetents multiplied by20°. Next, in block 162, in order to compensate for drift between amechanical angular position and its corresponding magnetically measuredposition, a new θ_(R) is determined by adding the products of(θ_(R)×0.8) and (θ_(T)×0.2). In many systems, especially digital outputtype systems, alignment between the mechanical detent positions and thesensing system is critical. In optical systems, alignment of the opticalreflective/absorptive material, the optical emitter/sensor andmechanical detent mechanism is crucial. If proper alignment is notachieved, shaft rotation can be erroneously detected and actual rotationmay go undetected. Marginal alignment may result in erratic output whenthe system is subject to vibration.

[0048] Since the instant encoder embodiment utilizes a high resolutionanalog vector of x and y to sense the knob/shaft angle, alignmentbetween the actual and measured detent positions is achieved in softwareby applying an offset to the reference angle. Most encoders have amis-alignment at the shaft's zero degree point (mechanical zero ispurely arbitrary) with the corresponding magnetically measured zerodegree point. In the present embodiment, at system initialization, thereference angle θ_(R) is set to the current magnetically measured angle.In a perfect system, after intial “alignment”, no further adjustmentswould be necessary. However, with errors in the mechanical detentmechanism, magnet, magnetic sensor alignment etc., the detents may notbe exactly 20° apart and the magnetic angle may be distorted. To reducethe effects of these errors, the present embodiment provides for theangle reference slowly to drift to the current magnetic angle by theexecution of block 162 through a number of cycles. If the knob/shaft isin any detent for a long enough period of time, the error is decayed tozero. Then, when the knob is rotated to the next detent, the angle erroris only the error between the detents—not an accumulated error fromprevious detents. Also, when the reference angle drifts to the currentmagnetic angle, the system is highly immune to noise. The noise on thesignal would have to be ˜½ the angle between detents for erroneousdetent count to occur. Likewise, as the system wears or the shaftfriction increases such that it does not stop precisely at a detent, thesystem self-aligns preventing erroneous detent counts.

[0049] Also, block 162 accumulates the ΔDetents determined for thecurrent execution cycle in a detent counter DCOUNT. Next, in block 164,the program stores in designated registers of the processor 102, thecalculated knob rate, push, release and accumulated detent counts DCOUNTand other parameters calculated during the current execution cyclebefore returning to wait for the next execution cycle. Also, if thedecisional block 150 determines that the time boundary between rough andfine computations has not been reached, then the instructional blocks152-164 which perform the fine computations are by-passed and theprogram routine waits for the next execution cycle. Accordingly, in thepresent embodiment, the fine computations, which may be computationalburdensome to the processor 102, are not conducted each execution cycle,but rather only during selected execution cycles in order to alleviatethe processing burden on the processor 102.

[0050] When resolving the knob position, both rotationally and axially,there are two main issues to consider. First, the process should beexecuted often enough such that it does not miss any user inputs, andthat it accurately represents the magnitude of the user input (it doesnot miss counting detents). Second, user feedback, such as a number on adisplay or display brightness should be updated fast enough that theuser sees a direct response to his input. In the case of the secondissue, updating the user feedback, the preferred update rate isconsiderably slower than that which is preferred in the first issue.

[0051] The exemplary software flowcharts depicted in FIGS. 9A through 9Ccontain two processes that address (1) keeping track of all knobchanges, and (2) updating the user feedback. The first process isdepicted in the blocks starting at “S” and continuing through block 150.In this process, a crude angular knob shaft position is determined byresolving angular position into quadrants using the signs of the x and ysignals from the magnetic sensors. Also, the knob's axial position isdetermined by the square root of the sum of the squares of signals x andy. Alternately, the shaft position may be determined by the sum of thesquares to reduce computational requirements. In this process, by usinginteger math, the computation time is minimized. The interval over whichthis process could be performed is a function of the maximum knobrotation rate. A minimum execution cycle rate can be calculated usingthe following equation ^(Interval=15/RPM). For example, for an accuratetrack of a shaft rotating at 3000 RPM, the interval would be N=5milliseconds.

[0052] The second process is depicted in the flowchart of FIG. 9C fromblock 152 to 162. In this second process, the shaft or knob angle isfinely resolved within five degrees or better depending on system errorsand calibration. The knob rate term is also calculated. The output ofthis process is used as the input to other processes, like displayroutines, for example, where the user may be adjusting a specificparameter such as a display brightness level. This process typicallyrequires more computation than the first process since it involves thecomputation of an arctangent and the knob rate term with filtering.However, since a user update interval of M=50 mS or more is acceptable,this process will typically run once for every ten times process oneruns.

[0053] Thus, it is shown that the processor may independently resolvethe axial and rotational movement of the knob shaft based on theforegoing described program execution. An example of this independenceof computed quantities is shown graphically by the illustration of FIG.10. Referring to the graph of FIG. 10, suppose the encoder is in theundepressed state R at a rotational angle θ1 initially, and thendepressed. Consequently, the magnetic field strength magnitude changesfrom M1 to M2 and the ratio, i.e. M2/M1, becomes greater than the upperlimit threshold (refer to block 126). Thus, the processor 102 detectsthe axial movement and registers the new state D of the encoder. Then,for example, suppose the encoder is rotated from angle θ1 to angle θ2while depressed. In this new state (D,θ2), the magnitude of thedepressed shaft may not be exactly the same as it was before, i.e.M4≠M2. However, the ratio of the present magnitude to the last magnitudeM1 will provide the same state, i.e. the depressed state. Accordinglythere is no change in the state of the axial movement. However, there isregistered a change in rotational movement from θ1 to θ2. Now, supposewhile in the state of θ2, the shaft is released and returns to themagnitude M3. Even though the magnitude M3 may be slightly differentfrom M1, the processor still detects the ratio of M3/M4 to be below thelower threshold and determines the axial state to be the release stateR. In this manner, the processor 102 may determine the axial movement ofthe shaft of the encoder independent of the rotational movement and viceversa.

[0054] In FIG. 11 is depicted a cross sectional illustration of analternate embodiment of the present invention. Referring to FIG. 11, amember 165 of a ferrous material is disposed in the housing cavity 18against the upper wall thereof. The member 165 may be a ferrous backingplate, for example, and inserted into the cavity 18 through the opening16 of the housing 10 and press fitted into the upper wall thereof. Ashaft member 166 of a non-ferrous material is slidably disposed in theopening 20 of the housing 10 rendering a bottom portion thereof in thecavity 18. In the housing opening 20, between the shaft 166 and housing10 is disposed a sleeve bearing 167 which extends into the cavity 18 andseparates the non-ferrous shaft 166 from the ferrous backing plate 165.Attached to the bottom portion of the shaft 166 is a permanent magnet168 which, for the present embodiment, may be a ring magnet having oneor more pole pairs, for example, and disposed about the periphery of thebottom portion of the shaft 166. The shaft 166 is held axially in placeat the bottom of the bearing 167 by the magnetic attraction forcebetween permanent magnet 168 and the backing plate 165 in the housingcavity 18. In the present embodiment, the permanent magnet 168 is of ahigh energy-product magnet type which may be comprised of a SamariumCobalt material, for example. Accordingly, the permanent magnet 168 ofthe shaft 166 is attracted to the backing plate 165 with a relativelyhigh magnetic attraction force.

[0055] Thus, in operation, when an external force is applied to the topend of the knob shaft 166 to depress the shaft into the cavity 18 of thehousing 10, the magnetic attraction force between the permanent magnet168 on the shaft member 166 and the backing plate 165 resists thedepressive push on the shaft until the external force overcomes themagnetic attraction force or force threshold. Once the force thresholdis reached, the knob shaft 166 slidably moves downward in the sleevebearing 167 and is displaced axially from its magnetically heldposition, producing a gap between the permanent magnet 168 and backingplate 165 in the cavity 18. As the gap increases, the magneticattraction or pull force of the permanent magnet 168 is reduced.Accordingly, the magnetic attraction force drops off with displacement,i.e. the gap, permitting the knob shaft 166 to travel to a fullydepressed position resulting in a “snap action” feel. When the externalforce on the knob shaft is released, the magnetic attraction or pullforce generated by the permanent magnet 168 with the plate 165 will snapthe shaft back axially to its juxtaposed position against the sleevebearing 167.

[0056] While this aspect of the present invention is exemplified using apush switch embodiment as described hereabove, it is understood that bysimply rearranging the switch elements that the same inventiveprinciples will also apply to a pull switch. Moreover, while anattractive magnetic force is used in the exemplary embodiment describedabove, it is further understood that a repulsive magnetic force could beused just as well by a rearrangement of members without deviating fromthe principles of the present invention.

[0057] According to another aspect of this alternate embodiment, theknob shaft 166 and its permanent magnet 168 are axially and/or rotatablymoveable in the housing cavity 18. The plurality of magnetic fieldsensors 94 are similarly disposed within the housing cavity 18 inproximity to the permanent magnet 168 of the shaft 166 and distributedangularly thereabout to sense the magnetic field strength of thepermanent magnet 168 based on the orientation thereof with respect tothe sensors 94. Each sensor 94 is capable of generating a signalrepresentative of the magnitude of the magnetic field strength sensedthereby. In the present embodiment, two magnetic field sensors aredistributed about the permanent magnet 168, ninety degrees apart. Themagnetic field sensors 94 of this embodiment may also include HallEffect devices that may be fixed in their respective positions andorientations with respect to the permanent magnet 168 in the cavity 18as illustrated in FIG. 11, by their disposition on the printed circuitboard 96 similarly affixed to the housing 10 at the opening 16. Theprinted circuit board 96 may also act as a bottom stop to the shaft 166as it is displaced from its magnetically held position by an externalforce. While the sensors 94 are shown upright or vertical to the axis ofthe shaft 166, it is understood that other orientations thereof such aslaying the sensors flat on the printed circuit board 96 will result insatisfactory sensor measurements in accordance with the principles ofthe present invention. In addition, while only two sensors are used forthe present embodiment, it is also understood that more than two sensorsmay be distributed about the permanent magnet 168 for greater accuracyor redundancy, if desired, without deviating from the present invention.Accordingly, this alternate embodiment may also be used as a suitableswitch for the multifunctional encoder apparatus described in connectionwith FIG. 8.

[0058] In another aspect of the present invention, the multifunctionalencoder as described hereinabove may operate as a controller for adisplay. In one embodiment of this aspect, as shown in FIG. 8, thedigital processor 102 may control a display 101. In this embodiment, thedigital processor 102 may respond to the press, rotate and releaseactuations of the encoder to provide control signals to the programroutines for the display 101. In this regard, reference is made to theprogram routines of FIGS. 9A and 9B. For example, when the encoder isdepressed as determined by the decisional block 126 a push count isincremented in block 130. For the display controller the incrementing ofthe push count may be a flag or signal to control the display programroutines to display a certain menu like that shown at 170 in the display101. While in this depressed state, if the encoder shaft is rotatedthrough a predetermined incremental angle change as determined, forexample, by block 154, then a detent count is altered which may be aflag or a control signal to the display program routines to scrollthrough the menu until the display results in a desired menu item.Thereafter, to select the menu item the encoder shaft is merelyreleased. The release of the shaft is detected by the decisional block128 which increments the release count in block 132 which may be a flagor a control signal to the display program routines to select that menuitem.

[0059] Also, as a display controller, the multifunctional encoder may beused to enter a numeric value through the display 101. For example,suppose the numeric value as depicted in FIG. 8A is displayed on thedisplay 101 in response to the press, rotate and release functions ofthe multifunctional encoder. Once the numeric value is present andselected, then the value may be changed based again on additional press,rotate and release actuations of the encoder. For example, a depressionof the shaft 60 may cause the selection of one of the digits in thenumerical value such as shown by the boxed digit in FIG. 8A. Onceselected, the boxed digit may be incremented or decremented based on arotation of the encoder shaft as determined by for example decisionalblocks 155 and 156 . If the change in angle rotation AO is in aclockwise direction, the number of detents determined in block 156 couldbe utilized as a flag or a control signal to the display programroutines to increase the value accordingly. Thus, the value may continueto be increased as the rotational angle of the shaft moves clockwisethrough one or more detents, for example. Likewise, the selected digitmay be decreased by rotating the shaft counterclockwise through one ormore detents as determined by the instructional block 157 which could beutilized as a flag or a control signal to the display program routinesto decrease the digit accordingly. Once the desired digit value isachieved, the shaft may be released and depressed again to allow thenext digit to be boxed and changed in value. For a rough rather than afine change, the quadrant changes as determined by blocks 142, 144 and146 may be similarly utilized for increasing or decreasing a numericvalue. In this manner, the multifunctional decoder may be used to enternumeric values as well as navigate menus of a different variety.

[0060] In one embodiment of the multifunctional encoder used as adisplay controller, at least one multifunctional encoder is disposed ata bezel 180 of the display 101 as shown in the perspective views ofFIGS. 5 and 6. In this embodiment, the housing of the at least onemultifunctional encoder is integral to the bezel 180 of the display. Inan alternate embodiment of the display controller aspect, the displaybezel 180 may include two multifunctional encoders, one disposed on eachside, which is illustrated by the top view 190 and side views 192 and194 of FIG. 12. Each multifunctional encoder for this alternateembodiment may be the same as or equivalent to that described hereabove.In other words, the digitizer 104 and digital processor 102 canaccommodate the sensor signals of one or more additional multifunctionalencoders and the program routine for each would be the same as orequivalent to that described in connection with the flowcharts of FIGS.9A through 9C. It is understood however that the control signalgenerations of one multifunctional encoder may cause the display programroutines to perform one set of functions and the control signalsresulting from the actuations of another multifunctional encoder mayresult in control signals that cause the display program routines toperform another set of functions. However, the principals of the presentinvention remains substantially the same and keeping track of thesedifferent display functions is merely a software bookkeeping endeavor.

[0061] While the various aspects of the present invention have beendescribed in connection with the embodiments described hereinabove, itis understood that the present invention should not be limited to anyspecific embodiment but rather construed in breadth and broad scope inaccordance with the set of claims appended hereto.

What is claimed:
 1. A switch with magnetic snap action comprising: ahousing having top and bottom sides and a cavity, said housing includingan opening on the top side that extends to said cavity: at least onepermanent magnet fixedly disposed with respect to said housing in saidhousing cavity; and a knob shaft including a top portion that isslidably disposed through said housing opening, and a bottom portiondisposed in the housing cavity and including a member comprised ofmagnetically attractive material, said knob shaft being held axially ina first position by a magnetic force between said shaft member and saidat least one permanent magnet, said knob shaft being displacable fromsaid first position for as long as said magnetic force is overcome by anexternal force applied to said knob shaft, whereby upon release of saidexternal force, said knob shaft snapping back to said first position bysaid magnetic force.
 2. The switch of claim 1 including a bushingdisposed in the housing opening, and including a hollow openingcentrally located and extending axially therethrough; wherein the knobshaft is slidably and rotatably disposed in said bushing opening; andwherein the knob shaft and bushing include a detent communicatingmechanism therebetween to permit the knob shaft to be rotated from onedetent position to another in the opening of the bushing.
 3. The switchof claim 2 wherein the detent communicating mechanism includes aplurality of ball bearings disposed about the periphery of the bushingand protruding radially through the wall of the bushing to be alignedaxially with a plurality of axial grooves on the peripheral surface ofthe knob shaft, said ball bearings rendering detent positions when atleast one of said ball bearings come in contact with at least one of theaxial grooves as the knob shaft is rotated in the opening of thebushing.
 4. The switch of claim 3 wherein the bushing includes at leastone row of ball bearings uniformly spaced about its periphery.
 5. Theswitch of claim 3 wherein the knob shaft includes more grooves thanthere are ball bearings disposed about each row of the bushing.
 6. Theswitch of claim 1 including a bushing comprising a top portion disposedin the housing opening, and a bottom portion that is disposed in thehousing cavity and including the at least one permanent magnet attachedthereto, said bushing including a hollow opening centrally located andextending axially therethrough; wherein the knob shaft is slidablydisposed in said bushing opening with its member being juxtaposed withthe bottom portion of said bushing.
 7. The switch of claim 6 wherein theat least one permanent magnet includes a plurality of permanent magnets;wherein the bottom portion of the bushing includes a plurality ofcutouts uniformly spaced around the periphery thereof to accommodatesaid plurality of permanent magnets; and wherein the shaft member isdisc shaped with a flat surface thereof in juxtaposition with the bottomportion of the bushing and a diameter extending to at least thepermanent magnets of the bottom portion of the bushing so that said flatsurface is in magnetic contact with the plurality of permanent magnets.8. The switch of claim 7 including a second member of magneticallyattractive material disposed annularly between the permanent magnets ofthe bottom portion of the bushing and the housing cavity and affixed tothe housing cavity; and wherein the permanent magnets are affixed to thebottom portion of the bushing and are held in axial position withrespect to the housing by magnetic attraction to said second member. 9.The switch of claim 8 wherein the second member includes a flux washerof ferrous material.
 10. The switch of claim 7 wherein the permanentmagnets are arranged so that the North and South poles thereof areaxially aligned with the bushing in an alternating pattern around theperiphery thereof.
 11. The switch of claim 1 including a stop memberdisposed in the housing cavity to limit displacement of the knob shaftaway from the first position.
 12. The switch of claim 11 wherein thestop member includes a flux ring affixed around the inner periphery ofthe housing cavity.
 13. The switch of claim 1 wherein the housingincludes another opening on the bottom side that opens into the cavityto permit assembly of the elements of the switch to the housing.
 14. Amethod of assembling a switch comprising the steps of: creating a firstopening in a bottom side of a housing and a cavity within the housinginto which said first opening extends; creating a second opening in atop portion of the housing which extends to the cavity, said secondopening being smaller in width than said first opening; affixing a fluxwasher around an inner periphery of said cavity through said firstopening; disposing a top portion of a bushing through said firstopening, said cavity and through said second opening of the housing torender a bottom portion of the bushing within the flux washer; disposinga plurality of permanent magnets into cutouts around the periphery ofthe bottom portion of the bushing in an annular space between the bottomportion and the flux washer; and disposing a top portion of a knob shaftthrough said first opening, said cavity and an opening in the bushing torender a disc shaped member of a bottom portion of the knob shaftcomprised of a magnetic material in juxtaposition with the bottomportion of the bushing and form a magnetic connection with the pluralityof permanent magnets thereof.
 15. The method of claim 14 wherein thestep of affixing the flux washer includes the step of press fitting theflux washer to the inner periphery of the housing cavity so that it isaxially aligned with the second opening of the housing.
 16. The methodof claim 14 including the step of forming cutouts around the peripheryof the bottom portion of the bushing of a shape to accommodatecontiguously the shape of the permanent magnets.
 17. The method of claim14 including the step of disposing a stop member in the cavity to limitdisplacement of the knob shaft from its juxtaposed position with thebushing.
 18. A switch with magnetic snap action comprising: a housinghaving top and bottom sides and a cavity; a plate of magneticallyattractive material fixedly disposed at an inside periphery of saidhousing cavity; a knob shaft including a top portion that is slidablydisposed through said housing opening, and a bottom portion disposed insaid housing cavity and including a permanent magnet, said knob shaftbeing held axially in a first position with respect to said housing by amagnetic force between said permanent magnet and said plate, said knobshaft being slidably displacable from said first position for as long assaid magnetic force is overcome by an external force applied to saidknob shaft, whereby upon release of said external force, said knob shaftsnapping back to said first position by said magnetic force.
 19. Theswitch of claim 18 wherein the knob shaft is comprised of a non-ferrousmaterial.
 20. The switch of claim 18 wherein the plate comprises abacking plate of ferrous material that is disposed around the insideperiphery of the housing cavity.
 21. The switch of claim 18 wherein thepermanent magnet includes a ring magnet disposed around the bottomportion of the knob shaft.
 22. The switch of claim 18 including a sleevebearing disposed between the knob shaft and housing in the housingopening, said sleeve bearing extending into the housing cavity aroundthe periphery of the knob shaft; wherein the plate includes a backingplate of ferrous material that is disposed between the sleeve bearingand housing in the housing cavity; and wherein the permanent magnetincludes a ring magnet disposed around the bottom portion of the knobshaft below the sleeve bearing and in juxtaposition with the backingplate.
 23. An encoder apparatus comprising: a housing including a cavityand an opening extending from the cavity to the top of the housing: aknob shaft including an upper portion disposed through the housingopening, and a lower portion disposed in the cavity and including apermanent magnetic magnetized with at least one set of North-Southmagnetic poles, said knob shaft and its permanent magnet being rotatablymovable in the housing cavity; a plurality of magnetic field sensorsdisposed within the housing cavity in proximity to said permanent magnetand distributed angularly thereabout to sense the magnetic fieldstrength of said permanent magnet based on the orientation of thepermanent magnet with respect to said sensors, each sensor forgenerating a signal representative of the magnitude of the magneticfield strength sensed thereby; and a processor for processing saidsensor signals to resolve rotational movement of the knob shaft.
 24. Theencoder apparatus of claim 23 wherein the magnetic poles of saidpermanent magnet being oriented transverse to the shaft axis.
 25. Theencoder apparatus of claim 23 wherein said plurality of magnetic fieldsensors include two sensors distributed about the permanent magnetninety degrees apart.
 26. The encoder apparatus of claim 25 wherein themagnetic field sensors include Hall Effect devices.
 27. The encoderapparatus of claim 23 wherein the processor includes means fordetermining a rotational angle of the shaft from the sensor signals. 28.The encoder apparatus of claim 27 wherein the processor includes meansfor determining rotational movement from a change in rotational angle ofthe shaft determined by the processor.
 29. The encoder apparatus ofclaim 28 wherein the processor includes means for causing a count changebased on the direction of rotational movement determined by theprocessor.
 30. The encoder apparatus of claim 27 wherein the processorincludes means for causing a count change based on a function of thedetermined change in rotational angle of the shaft and a predeterminedincremental change in rotational angle.
 31. The encoder apparatus ofclaim 30 wherein the processor includes means for adjusting a rate atwhich the count changes commensurate with the rotational movement of theknob shaft.
 32. The encoder apparatus of claim 30 wherein the processorincludes means for determining a knob rate based on a function of thecount changes and a predetermined constant.
 33. The encoder apparatus ofclaim 27 wherein the processor includes means for converging therotational angle determined from the sensor signals to a correspondingmechanical rotational angle, thereby reducing any error therebetweencreated by mechanical misalignment over time.
 34. The encoder apparatusof claim 28 wherein the processor includes means for generating acontrol signal based on the direction of rotational movement determinedby the processor.
 35. The encoder apparatus of claim 28 wherein theprocessor includes means for generating a control signal based on afunction of the determined change in rotation angle of the shaft and apredetermined incremental change in rotation angle.
 36. The encoderapparatus of claim 23 wherein the processor includes means for selectingbetween crude and fine processing of sensor signals to resolverotational movement of the knob shaft.
 37. The encoder apparatus ofclaim 23 wherein the sensor signals are analog signals; and wherein theprocessor includes a digitizer for digitizing the analog sensor signalsinto digital signals; and wherein the processor is a digital processorfor processing said digitized sensor signals.
 38. The encoder apparatusof claim 37 wherein the digitizer is controlled by the processor todigitize the sensor signals at predetermined time intervals. 39.Multifunctional encoder apparatus comprising: a housing including acavity and an opening extending from the cavity to the top of thehousing: a knob shaft including an upper portion disposed through thehousing opening, and a lower portion disposed in the cavity andincluding a permanent magnetic magnetized with at least one set ofNorth-South magnetic poles, said knob shaft and its permanent magnetbeing axially and rotatably movable in the housing cavity; a pluralityof magnetic field sensors disposed within the housing cavity inproximity to said permanent magnet and distributed angularly thereaboutto sense the magnetic field strength of said permanent magnet based onthe orientation of the permanent magnet with respect to said sensors,each sensor for generating a signal representative of the magnitude ofthe magnetic field strength sensed thereby; and a processor forprocessing said sensor signals to independently resolve axial androtational movement of the knob shaft.
 40. The multifunctional encoderapparatus of claim 39 wherein said plurality of magnetic field sensorsinclude two sensors distributed about the permanent magnet ninetydegrees apart.
 41. The multifunctional encoder apparatus of claim 40wherein the magnetic field sensors include Hall Effect devices.
 42. Themultifunctional encoder apparatus of claim 39 wherein the processorincludes means for determining a rotational angle of the shaft from thesensor signals; and means for determining a magnitude of the magneticfield strength from the sensor signals.
 43. The multifunctional encoderapparatus of claim 42 wherein the processor includes means fordetermining axial movement of the shaft from a change in magnitude of avector sum of said magnetic field strength magnitudes; and means fordetermining rotational movement of the shaft from a change in a functionof the ratio of the magnetic field strength magnitudes; said axialmovement of the shaft is determined by the processor independent of thedetermination of said rotational movement of the shaft and vice versa.44. The multifunctional encoder apparatus of claim 43 wherein theprocessor includes means for causing a count change based on thedirection of axial movement determined by the processor.
 45. Themultifunctional encoder apparatus of claim 43 wherein the processorincludes means for causing a count change based on the direction ofrotational movement determined by the processor.
 46. The multifunctionalencoder apparatus of claim 43 wherein the processor includes means forcausing a count change based on a function of the determined change inrotation angle of the shaft and a predetermined incremental change inrotation angle.
 47. The multifunctional encoder apparatus of claim 46wherein the processor includes means for determining a knob rate basedon a function of the count changes and a predetermined constant.
 48. Themultifunctional encoder apparatus of claim 43 wherein the processorincludes means for generating a control signal based on the direction ofaxial movement determined by the processor.
 49. The multifunctionalencoder apparatus of claim 43 wherein the processor includes means forgenerating a control signal based on the direction of rotationalmovement determined by the processor.
 50. The multifunctional encoderapparatus of claim 43 wherein the processor includes means forgenerating a control signal based on a function of the determined changein rotation angle of the shaft and a predetermined incremental change inrotation angle.
 51. The multifunctional encoder apparatus of claim 39wherein the sensor signals are analog signals; and wherein the processorincludes a digitizer for digitizing the analog sensor signals intodigital signals; and wherein the processor is a digital processor forprocessing said digitized sensor signals..
 52. The multifunctionalencoder apparatus of claim 51 wherein the digitizer is controlled by theprocessor to digitize the sensor signals at predetermined timeintervals.
 53. A controller for a display comprising: at least onemultifunctional encoder comprising: a housing including a cavity and anopening extending from the cavity to the top of the housing: a knobshaft including an upper portion disposed through the housing opening,and a lower portion disposed in the cavity and including a permanentmagnetic magnetized with at least one set of North-South magnetic poles,said knob shaft and its permanent magnet being axially and rotatablymovable in the housing cavity; and a plurality of magnetic field sensorsdisposed within the housing cavity in proximity to said permanent magnetand distributed angularly thereabout to sense the magnetic fieldstrength of said permanent magnet based on the orientation of thepermanent magnet with respect to said sensors, each sensor forgenerating a signal representative of the magnitude of the magneticfield strength sensed thereby; and a processor governed by said sensorsignals to generate control signals for controlling said display. 54.The controller of claim 53 wherein the processor includes means forprocessing the sensor signals of the at least one multifunctionalencoder to independently resolve axial and rotational movement of theknob shaft of each said encoder.
 55. The controller of claim 54 whereinthe processor includes means for generating control signals for thedisplay based on the axial and rotational movement resolutions of theknob shaft of each said encoder.
 56. The controller of claim 54 whereinthe processor includes means for determining a rotational angle of theshaft of each said encoder from the sensor signals thereof; and meansfor determining a magnitude of the magnetic field strength of each saidencoder from the sensor signals thereof.
 57. The controller of claim 56wherein the processor includes means for determining axial movement ofthe shaft of each said encoder from a change in said magnetic fieldstrength magnitude thereof; and means for determining rotationalmovement of each said encoder from a change in rotational angle of theshaft thereof; said axial movement of the shaft is determined by theprocessor independent of the determination of said rotational movementof the shaft and vice versa for each said encoder.
 58. The controller ofclaim 57 wherein the processor includes means for generating a controlsignal for the display based on a function of the determined change inrotation angle of the shaft of each said encoder and a predeterminedincremental change in rotation angle corresponding thereto.
 59. Thecontroller of claim 54 wherein the processor includes means forgenerating a control signal for the display based on the direction ofaxial movement of the shaft of each said encoder determined by theprocessor.
 60. The controller of claim 54 wherein the processor includesmeans for generating a control signal for the display based on thedirection of rotational movement of each said encoder determined by theprocessor.
 61. The controller of claim 53 wherein the at least onemultifunctional encoder is disposed at a bezel of the display.
 62. Thecontroller of claim 53 wherein each housing of the at least onemultifunctional encoder is integral to a bezel of the display.
 63. Thecontroller of claim 53 wherein the controller comprises twomultifunctional encoders.